A trigger group includes all parts of the firearm that initiate the firing of the bullet. Parts include the trigger, which is usually a lever that is tripped by one or more fingers of the firing hand; the sear, which holds the hammer back until the trigger has been pulled; a disconnector, which keeps the hammer in place until the trigger is released and the sear takes over after a cycle of semi-automatic fire has occurred; and several springs throughout the group. The sear may be a separate part or can be a surface incorporated into the trigger. As the trigger is pulled, the sear slips, allowing the hammer to strike the firing pin to discharge a round.
A release trigger releases the hammer or striker when the trigger is released by the shooter rather than when it is pulled, thereby firing a round not when the trigger is pulled, but upon trigger release. An existing approach to a trigger system that does not fire with trigger pull and fires one round with trigger release is disclosed in U.S. Pat. No. 2,027,950 to Young. Young's trigger system, and release triggers generally, are largely used on shotguns intended for trap and skeet shooting. However, Young's trigger system suffers from multiple disadvantages. First, there is no way to change the mode of firing from release trigger to standard semi-automatic firing. Second, there is no provision for using Young's trigger system in other popular weapons systems, such as the AR-15, M-16, and AR-10 platforms.
U.S. Pat. Nos. 8,820,211 and 8,667,881 to Hawbaker disclose a trigger system with a selector that allows the user to choose between two modes and rates of fire. One mode is firing one round with a trigger pull and resetting with trigger release, and the second mode is firing one round with trigger pull, and firing a second round with trigger release. Hawbaker's trigger must be pulled fully rearward or released fully forward to operate and utilizes two disconnectors. Hawbaker has the disadvantage of requiring two selectors with two positions each (a safety selector and a mode selector), with the mode selector being located on the trigger. The location of the mode selector on the trigger is particularly disadvantageous since the setting of the mode selector could be unintentionally changed by the user while reaching for the trigger.
Therefore, a need exists for a new and improved trigger group for semi-automatic firearms that enables the firearm to switch between safe, semi-automatic, and release trigger modes. In this regard, the various embodiments of the present invention substantially fulfill at least some of these needs. In this respect, the trigger group for semi-automatic firearms according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in doing so provides an apparatus primarily developed for the purpose of providing a trigger group for semi-automatic firearms that enables the firearm to switch between safe, semi-automatic, and release trigger modes.